Sync with inBackground doesnt complete if curator client is closed

Calling sync with a callback on a closed client doesnt fail synchronously. Nor is the callback invoked with failure details.

Following is the code snippet to reproduce the issue:

client.close();

client.sync().inBackground(callback, executor).forPath(path);

This works correctly for other api calls like `getData` etc where the call fails synchronously.

Expected Behaviour:

Callback should have been called with IllegalStateException or any other appropriate failure. Or attempt to call sync on a closed client should have failed synchronously. But neither does the api fail nor is the callback invoked unlike it is for all other types of calls.